Poor performance of ZED-X20P

GPS/GNSS
1

Hi!

I’m working with the Sparkfun module ZED-X20P with the U.FL antenna Taoglas ADFGP.50A.

I have already modified the RF jumper to power supply the antenna. In open skies, with the default settings (configured via U-Center 2, from Ublox), I set the voltage control (CFG-HW-ANT_CFG_VOLTCTRL) to True. Bands 3 and 6 are deactivated:

Normally, doing a cold start and after 20 minutes powered-on, I get:

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Which is much poorer than I expected. I have also tried with another antenna, Taoglas AGGP.25F, with similar results.

As comparison, using a Ublox Max-M10S, with just band L1 and the same antenna, after a couples of minutes I get 3d-fix with more than 10 satellites used.

What may be happening? Is there any parameter I should set for this GNSS device and this antenna?

Thank you very much,
Pablo.

2

Hi Pablo (@PabloGA ),

Can you please tell us more about these modifications? If the antenna is not being powered correctly, that may explain the low signal levels.

Best wishes,
Paul

3

Hi Paul,
just soldered it:

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I have also tried with the Taoglas Quad Helix Antenna (also through the U.FL connector using an SMA-U.FL adapter), and it works great with it.

Thanks,

Pablo

4

Hi Pablo (@PabloGA ),

OK - thank you.

I read through the datasheet for the Taoglas ADFGP.50A antenna and I could not find any information about what voltage it needs or how much current it draws.

The antenna circuit includes a 10 Ohm resistor to protect against short circuits:

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That could be limiting the voltage to the antenna, if it is drawing slightly more current than other antennas.

If you are confident enough to try it, you could try shorting out that resistor to ensure the antenna gets the full 3.3V. I would recommend trying with a jumper wire first. Connect the wire over the resistor and watch the signal levels in u-center. If the levels increase, you have found the issue. But please be careful. Take ESD precautions. You are working close to the module 's RF path. You need to work carefully to avoid damaging the RF input.

I hope this helps,
Paul

5

Hi Paul

Thanks for the hint.

I wired it, with the same result. Also checked the voltage, and it is 3.3V, so I guess the antenna is properly powered.

May it be a problem of any incompatibility between the module and the antenna?

Best Regards,
Pablo

6

When you put the solder bridge on the jumper, did you cut the trace that connects the other two pads?

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Also, there’s a lot of solder flux on your board, you might try cleaning that off. It could possibly be conducive at RF frequencies.

7

Hi @YellowDog

I cut that trace before soldering the pads. I have tested if again after cleaning it up, and same behavior.

I will probably end up using the SMA Taoglas Quad Helix, given that it works well with it.

Thanks for your help!

Pablo

8

Thanks for the update Pablo,

I suspect it is a power / voltage issue. But, like I say, I could not find any information in the datasheet about what voltage that antenna needs or how much current it draws. If it needs more than 3.3V, that would explain your low signal levels. (Your signal levels are about 10dB below where they should be. Assuming you are testing outdoors, with a clear view of the sky?)

Best,
Paul